View Single Post
Old 01-02-2013, 02:35 PM   #1 (permalink)
EcoModding Apprentice
HypermilerAX's Avatar
Join Date: Apr 2011
Location: Southern France
Posts: 159

AX - '95 CitrŲen AX

307 - '04 Peugeot 307 SW
Thanks: 12
Thanked 67 Times in 37 Posts
"Do-it-all" excel calculator


I decided to share this excel sheet I have progressively made for myself.
I had post this in the online tool calculator thread but since it has other features, I thought it deserves its own thread.
It's an excel sheet to calculate lots of things, including the features of the online tool. At the beginning, I made the sheet to calculate my wattage on the bike and used it for the car when I began driving.
It's all metric for now, maybe I'll do a US-version if there are many requests. Only the fields squared in red should be changed according to your car.
To calculate the required power, it asks for mass, Crr, CdA, speed, air density but also slope. Air density can be either entered directly or calculated with temperature, pressure and humidity.
It, then, displays :
- each force and power (rolling, aero, gravity) with their respective part
- power needed (watt and hp)
- torque according to your gearing ratio (to be entered)
- BMEP in bar for BSFC (according to torque and engine displacement to be entered)
- fuel consumption in both l/100 km or mpg (US) according to either efficiency in % or BSFC in g/kWh

The next tab is an acceleration calculator that can be used for P&G for example. You have to enter the power of your engine at each RPM. It would be ideal to have the power curve of your engine. By default, it's an engine giving 58 hp at 5000 rpm (power output is roughly supposed linear with RPM).
For each speed by 1 km/h increments, it displays :
- RPM (can be used with any of your gears if your enter the ratio)
- power to maintain speed
- spare power available to accelerate
- acceleration
- time to accelerate by 1 km/h
- 'instant' consumption (to be precise, you should have the exact power curve and BSFC map of your engine, values entered by default are random). It is constant because I chose a constant BSFC with RPM (at full load) which is not true and a linear power curve which might not be true as well.

You can then manually calculate the consumption during the pulse/glide phase and compare with constant speed or different speeds for P&G. You can calculate theoretical coastdown time during the glide phase with the next tab.
It works not bad. I tested a 0 to 100 km/h for my car. The calculator gives me 13,45 sec + 2 seconds for 2 gear changes, that's 15,45 sec. The official time is 15,7.
P&G between 85 and 95 km/h gives me 2,95 l/100 km vs 3,6 at 90 constant speed. But thatís ideal, I have observed that real life coastdowns are always worse than the theory.

Next tab is a Cd, Cr calculator with car and coastdown info.

Any feedback, critics, questions or new ideas are welcome. Have fun !

EDIT : little error. In second tab, column H : unit is L/100 km and not L/h.

Attached Files
File Type: xls calculator.xls (116.5 KB, 998 views)
CitroŽn AX 1.5 D 430.000 km
Peugeot 307 SW 2.0 HDI 136 195.000 km

Last edited by HypermilerAX; 01-09-2013 at 01:40 AM..
  Reply With Quote
The Following 3 Users Say Thank You to HypermilerAX For This Useful Post:
AndrzejM (01-02-2013), DieselX (01-02-2013), ECONORAM (01-02-2013)